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+On [[todo/auto-create_tag_pages_according_to_a_template]], [[chrysn]]
+suggests:
+
+> Instead of creating a file that gets checked in into the RCS, the
+> source files could be left out and the output files be written as
+> long as there is no physical source file (think of a virtual underlay).
+> Something similar would be required to implement alias directive,
+> which couldn't be easily done by writing to the RCS as the page's
+> contents can change depending on which other pages claim it as an alias.
+
+`add_autofile` could be adapted to do this, or a similar API could be
+added.
+
+This would also be useful for autoindex, as suggested on
+[[plugins/autoindex/discussion]]. I'd also like to use it for
+[[plugins/contrib/album]].
+
+One refinement I'd suggest is that if the transient page is edited,
+its transient contents are evaluated and used as the initial
+content for the edit box; after that, it'd become a static page. --[[smcv]]
+
+--------------------------
+
+[[!template id=gitbranch branch=smcv/transient author="[[smcv]]"]]
+[[!tag patch]]
+
+I had a look at implementing this. It turns out to be harder than I thought
+to have purely in-memory pages (several plugins want to be able to access the
+source file as a file), but I did get this proof-of-concept branch
+to write tag and autoindex pages into an underlay.
+
+This loses the ability to delete the auto-created pages (although they don't
+clutter up git this way, at least), and a lot of the code in autoindex is
+probably now redundant, so this is probably not quite ready for merge, but
+I'd welcome opinions.
+
+Usage: set `tag_underlay` and/or `autoindex_underlay` to an absolute path,
+which you must create beforehand. I suggest *srcdir* + `/.ikiwiki/transient`.
+
+Refinements that could be made if this approach seems reasonable:
+
+* make these options boolean, and have the path always be `.ikiwiki/transient`
+* improve the `remove` plugin so it also deletes from this special underlay
+
+>> Perhaps it should be something more generic, so that other plugins could use it (such as "album" mentioned above).
+>> The `.ikiwiki/transient` would suit this, but instead of saying "tag_underlay" or "autoindex_underlay" have "use_transient_underlay" or something like that?
+>> Or to make it more flexible, have just one option "transient_underlay" which is set to an absolute path, and if it is set, then one is using a transient-underlay.
+>> --[[KathrynAndersen]]
+
+>>> What I had in mind was more like `tag_autocreate_transient => 1` or
+>>> `autoindex_transient => 1`; you might conceivably want tags to be
+>>> checked in but autoindices to be transient, and it's fine for each
+>>> plugin to make its own decision. Going from that to one boolean
+>>> (or just always-transient if people don't think that's too
+>>> astonishing) would be trivial, though.
+>>>
+>>> I don't think relocating the transient underlay really makes sense,
+>>> except for prototyping: you only want one, and `.ikiwiki` is as good
+>>> a place as any (ikiwiki already needs to be able to write there).
+>>>
+>>> For [[plugins/contrib/album]] I think I'd just make the photo viewer
+>>> pages always-transient - you can always make a transient page
+>>> permanent by editing it, after all.
+>>>
+>>> Do you think this approach has enough potential that I should
+>>> continue to hack on it? Any thoughts on the implementation? --[[smcv]]
+
+>>>> Ah, now I understand what you're getting at. Yes, it makes sense to put transient pages under `.ikiwiki`.
+>>>> I haven't looked at the code, but I'd be interested in seeing whether it's generic enough to be used by other plugins (such as `album`) without too much fuss.
+>>>> The idea of a transient underlay gives us a desirable feature for free: that if someone edits the transient page, it is made permanent and added to the repository.
+>>>>
+>>>> I think the tricky thing with removing these transient underlay pages is the question of how to prevent whatever auto-generated the pages in the first place from generating them again - or, conversely, how to force whatever auto-generated those pages to regenerate them if you've changed your mind.
+>>>> I think you'd need something similar to `will_render` so that transient pages would be automatically removed if whatever auto-generated them is no longer around.
+>>>> -- [[KathrynAndersen]]